Spatio-Temporal Analysis of Urban Heat Island and Land Use/Land Cover Dynamics Using Remote Sensing and GIS: A Case Study of Varanasi, India

Abstract

Urban Heat Island (UHI) is among the most significant aspects of rapid urbanization and unplanned land use and development in developing cities. In the present study, spatio-temporal variation of intensity of Urban Heat Island (UHI) and its correlation with land use and land cover (LULC) change in Varanasi have been analyzed with the help of a Remote Sensing (RS) and Geographic Information System (GIS) techniques. Multi-temporal Landsat satellite imagery (2005, 2015, and 2025) were used to analyse the changes in Land Surface Temperature (LST), vegetation cover, built-up areas, moisture conditions and barren land distribution in the study area. Various spectral indices such as Normalized Difference Vegetation Index (NDVI), Normalized Difference Water Index (NDWI), Normalized Difference Built-up Index (NDBI) and Normalized Difference Bareness Index (NDBaI) were calculated to assess the environmental transformation and thermal characteristics of urban areas. The findings showed that there was a substantial increase in built-up surfaces and barren land with a decrease in the amount of vegetation cover and moisture-rich areas between the years 2001 and 2018. Spatial analysis indicated that comparatively higher LST values were found in urban dense areas while lower LST values were found in areas with vegetation cover and close to the River Ganga. The negative relationship between LST and NDVI/NDWI, along with positive relationships between LST and NDBI/NDBaI was found using correlation analysis, which suggests that built-up and exposed surfaces play a significant role in the creation of UHI. The results indicate that rapid urbanization has affected the environment and the need for sustainable urban planning, afforestation in urban areas, protection of water bodies and infrastructure that can adapt to climate change in order to reduce the effects of the Urban Heat Island in rapidly growing cities and make the urban environment more sustainable.

Introduction

This study investigates the spatio-temporal impact of urbanization on Land Use/Land Cover (LULC) changes and Urban Heat Island (UHI) intensity in Varanasi, India, using multi-temporal Landsat satellite imagery from 2005, 2015, and 2025. Rapid urbanization, population growth, and infrastructure development have transformed vegetated and agricultural lands into impervious built-up areas, increasing Land Surface Temperature (LST) and intensifying the Urban Heat Island effect. To assess these environmental changes, the study integrates Remote Sensing (RS) and Geographic Information Systems (GIS) with spectral indices including Normalized Difference Vegetation Index (NDVI), Normalized Difference Water Index (NDWI), Normalized Difference Built-up Index (NDBI), and Normalized Difference Bareness Index (NDBaI). These indices provide insights into vegetation health, surface moisture, built-up density, and barren land, enabling comprehensive evaluation of urban thermal behavior. Correlation analysis between LST and spectral indices further supports understanding of the relationship between urban expansion and environmental degradation.

The literature highlights that impervious urban surfaces increase heat storage while reducing evapotranspiration, making thermal remote sensing an effective approach for monitoring urban climate change. Previous studies have demonstrated strong negative correlations between vegetation (NDVI) and LST, while built-up surfaces (NDBI) and barren land (NDBaI) are positively associated with higher temperatures. However, research on medium-sized historic cities like Varanasi remains limited, particularly studies combining multiple environmental indices over a long-term period. This study addresses these gaps by integrating LST, NDVI, NDWI, NDBI, and NDBaI within a unified analytical framework over a 20-year period (2005–2025) to provide a comprehensive assessment of urban growth, environmental degradation, and UHI dynamics.

The methodology employs Landsat-5 TM (2005) and Landsat-8 OLI/TIRS (2015 and 2025) imagery with less than 5% cloud cover, supplemented by administrative boundaries, Google Earth imagery, and topographic data. Land use classification identifies four major categories: built-up areas, vegetation, water bodies, and barren land. Change detection analysis quantifies land transformations, while thermal infrared data are used to generate Land Surface Temperature maps for identifying urban thermal hotspots and UHI intensity.

The results reveal substantial urban expansion between 2005 and 2025, primarily at the expense of vegetation and open land. Built-up areas experienced the greatest increase, especially along transportation corridors and suburban regions, while vegetation declined significantly due to infrastructure development. This reduction in green cover weakened natural cooling through evapotranspiration, leading to increased sensible heat and intensified Urban Heat Island effects. Land Surface Temperature maps show a continuous rise in thermal intensity, with LST increasing from approximately 27°C to 45°C by 2025. High-temperature zones expanded across densely urbanized areas, whereas cooler temperatures remained concentrated around water bodies and green spaces due to their evaporative cooling effects. Overall, the study demonstrates that rapid urbanization has significantly altered Varanasi's landscape and thermal environment, emphasizing the need for climate-sensitive urban planning, green infrastructure development, and sustainable land management to mitigate Urban Heat Island impacts and enhance urban resilience.

Conclusion

In the present research, spatio-temporal variations in the intensity of Urban Heat Island (UHI) and Land Use Land Cover (LULC) of Varanasi city, India has been studied by employing multi-temporal Landsat satellite images as the data source and Remote Sensing and Geographic Information System (GIS) techniques. To assess the environmental changes due to high urbanization, the Land Surface Temperature (LST) and four very common spectral indices such as Normalized Difference Vegetation Index (NDVI), Normalized Difference Water Index (NDWI), Normalized Difference Built-up Index (NDBI), and Normalized Difference Bareness Index (NDBaI) were examined for the years of 2005, 2015, and 2025. The analysis revealed that there was significant alteration of the urban landscape in the 20 years under study. Built-up area and impervious surfaces continued to grow mostly at the cost of vegetation and open land, which shows the high rate of population growth, infrastructure development, and urbanization. The changes in land use had a marked effect on the thermal properties of the city and were also responsible for the gradual increase in the severity of the UHI phenomena. The trend of Land Surface Temperature was overall upward, with the largest values being recorded in urbanized areas that are highly developed in terms of the presence of impervious surfaces. On the other hand, comparatively low temperatures were recorded in the vegetated and water-dominated regions, such as the area along the River Ganga and urban green spaces. These findings emphasize the important role of natural ecosystems in regulating urban thermal environments. The correlation analysis also revealed a strong correlation between the environmental characteristics and the surface temperature. The relationships between NDVI, NDWI and LST were negative, supporting the fact that vegetation cover and higher moisture conditions show a strong ability to limit the thermal accumulation from evapotranspiration and evaporative cooling. NDBI and NDBaI, however, showed positive correlations with LST, suggesting that urban built-up areas and bare areas significantly add to the heat stress in urban environments.

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Copyright © 2026 Vikas Gautam. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.